GT dash noises
Perhaps - I say perhaps, its the same creaking noise that I had in my 156. After almost two years of searching / listening, I came to the solution of the problem !!
The dashboard is secured to the car body by means of several, of say 5-6 hex bolts, right under the windshield, and deep in the dashboard.
These bolts are only half threaded, the rest (closer to the top) are just thicker in diameter. Apparently, their length is a tad longer than it should be and when the dashboard rubs against the car body it produces the creaking sound.
I just added some rubber and/or metal washers to take up the gap, and the creaking noise stopped!!! (you may need a special hex wrench with a hole in the middle)
(A simple test, is that the noise stops when the dashboard warms up, as it expands and the expansion takes up the gap !!).
It worked for me in my 156, hope it works for you